Neuronal pathways which mediate specific mechanisms of color vision will be studied in the retina of goldfish and ratfish. Individual cells will be impregnated with silver chromate by the Golgi method. Light and electron microscopy will be employed to analyze patterns of connections between photoreceptors, bipolar and horizontal cells. Uptake or binding of radioactively labeled putative transmitters and synaptic blockers, electrical recording from single cells, and immunobiochemical assays and localizations will be employed to indicate which cells and synapses may employ or respond to acetylcholine, glycine, thyrotropin releasing hormone and somatostatin. Developing retinas will be examined to analyze neurogenesis and synaptogenesis. A microcomputer-based data acquisition and graphics system will be applied to analysis and recontruction of serially-sectioned cells and synapses.